Nicotinic acid is an oxide of nicotine and is extensively present in animal and plant bodies as a water-soluble vitamin, which is also called vitamin B complex, niacin or vitamin B3. Deficiency of nicotinic acid may result in pellagra disease or neuropathies. Nicotinic acid is generally present in the form of nicotinic acid amide co-enzyme (NAD, NADP) in the living body, and participates in the oxidation-reduction reaction.
Nicotinic acid as usefully utilized in food and medicinal products can be prepared by means of chemical synthetic method or biological producing method. Chemical synthesis of nicotinic acid has been generally accomplished through oxidation using 3-picolne as an oxidizing catalyst. Specifically, 2-methylpentanediamine (MPDA) is subjected to hyperthermal reaction (280 to 360° C.) by means of a catalyst to synthesize 3-picoline, and then 3-picoline is subjected to ammoxidation to produce 3-cyanopyrine, which is then hydrolyzed to synthesize niacinamide or nicotinic acid. Alternatively, nicotinic acid can be directly synthesized from 3-picoline through selective oxidation (Applied Catalysis A: General 280 (2005) 75-82). However, because chemical synthesis results in large quantities of toxic wastes including the catalyst, there is a need of thorough management and great expenses are required for disposal of wastes. In order to solve such problem the method for synthesizing niacin from 3-cyanopyridine using an enzyme has been developed. However, this method also has similar problems due to the use of 3-cyanopyrine which causes a generation of wastes in large quantities. Further, because pyrimidine used as a precursor has various derivatives, and thus, suffers from a great fluctuation in the supply and price thereof, this method may cause instability of niacin price.
In addition, other methods for producing nicotinic acid from quinolinic acid have been disclosed. Chinese Patent CN101353322C discloses the method for synthesis of nicotinic acid using quinolinic acid as the substrate through hydrothermal decarboxylation. The method for producing nicotinic acid proceeds by mixing quinolinic acid with deionized hot water in the ratio of 2:1 to 5:1 and then allowing the mixture to react at a high temperature of 150 to 250° C. and high pressure of 1 to 2 MPa for 5 to 60 minutes (Ind. Eng. Chem. Res. 2009, 48, 10467-10471). This method has an advantage in that no side product of the catalyst is produced, while it has also the problems that the reaction conditions are high temperature and high pressure of 150 to 250° C. and 2 MPa require high energy. All the established chemical synthetic methods use non-renewable materials derived from petroleum as the raw material, and therefore, are greatly influenced by environmental problems or the unit price of petroleum extraction.
In order to solve such problems involved in the chemical synthesis methods, methods for biologically producing nicotinic acid by means of renewable carbohydrate-derived materials has been studied. Biological production of nicotinic acid has been accomplished mainly through two kinds of synthetic pathway. The first one is a pathway to produce quinolinic acid from tryptophan as a starting material, and then biologically synthesize nicotinic acid from the quinolinic acid, and the other is a pathway to produce quinolinic acid from aspartic acid as a starting material, and then biologically synthesize nicotinic acid from the quinolinic acid. In general, eukaryotes biologically synthesize nicotinic acid through the pathway to synthesize nicotinic acid from tryptophan as the starting material, while prokaryotes utilize the pathway to synthesize nicotinic acid from aspartic acid as the starting material as the main pathway. Both pathways comprise quinolinic acid as the intermediate, and synthesize nicotinic acid by the action of quinolinate phosphoribosyltransferase (nadC), nicotinate-mononucleotide adenylyltransferase (nadD), NAD synthetase (nadE), NMN adenylyltransferase (nadR) and nicotinamidase (pncA) from quinolinic acid.
The method for biological production of nicotinic acid utilizing recombinant Escherichia coli or Corynebacterium glutamicum, which produce nicotinic acid through the aspartic acid pathway, has been reported. U.S. Pat. Nos. 6,692,946 and 6,689,587 disclose the methods for producing nicotinic acid by separating the nadA gene and nadC gene, which encode quinolinate synthetase and quinolinate phosphoribosyltransferase, respectively, from the Corynebacterium glutamicum (ATCC 13032) strain, and then, incubating host cells which over-express such genes. The amount of nicotinic acid produced by the methods for biological production of nicotinic acid as disclosed in said US patents is very low, below 100 mg/L. It is considered that the causes of this low production include transcriptional suppression by NadR, which is an NAD-related transcriptional repressor of nadB as the gene coding for aspartate oxidase and nadA as the gene coding for quinolinate synthetase (Gerasimova AV (2005). J Bioinform Comput Biol 3(4); 1007-19.), feedback inhibition of aspartate oxidase and NAD synthetase with NAD (Biol Chem Hoppe Seyler. 1990 March; 371(3):239-48), complexity of the reaction including the steps by NadB, NadA, NadC, as well as NadD, NadE, NadR and PncA, and the like.
The methods for biological production of nicotinic acid have the disadvantages in that the production yield of nicotinic acid is very low due to inhibition of the expression of enzymes involved in said biosynthetic pathways, feedback inhibition and complexity of reaction.